An attempt to increase the yield by promoting the growth of crops and increasing the yield per unit area is a task important in agricultural production. Usually, major three elements essential for plant growth, that is, nitrogen, phosphorus and potassium, and nutrient elements such as trace metal elements, are incorporated into a fertilizer and an additional fertilizer and supplied to plants, but the amount and yield of grown crops are generally limited even if the concentration of the nutrient elements in the fertilizer is increased, and by using the fertilizer in a larger amount, the nutrient elements come to be in excess in the soil thus worsening the balance of absorption and causing a reduction in plant growth, resulting in problems such as failure to achieve the intended increase in yield and failure to improve qualities such as sugar degree (Brix value) and freshness (greenness). Under these circumstances, combined use of various plant growth regulators has been carried out.
As the plant growth regulator, plant growth regulators represented by gibberellin and auxin are used in regulation of growth and morphogenetic reaction such as germination, rooting, elongation, flowering and fruit setting. Further, there are known techniques wherein a leaf spray using an oligosaccharide (JP-A 9-322647) or a liquid fertilizer containing sugars, minerals, amino acids, a seaweed extract or a microbial fermentation extract is sprayed onto leaves or applied in the form of a solution. JP-A 55-40674 discloses use of a C30 alcohol as a plant growth promoter. JP-A 2000-198703 discloses a plant activating agent containing a C12 to C24 monovalent alcohol. JP-A 2002-265305 discloses an agent for increasing the yield of crops, which contains a specific compound such as a C12 to 24 monovalent alcohol.